The previous BMI chart for children ages 2 to 19, published in 2000, is based on data from 1963 to 1980, but obesity and severe obesity in children has increased significantly since the eighties. More than 4.5 million children and teenagers had severe obesity in 2018, according to the CDC.
BMI is calculated using a mathematical formula that measures body fat, generally by dividing an individual’s height by their weight. For adults, a healthy BMI runs from 18.5 to 24.9, or 111 lbs. to about 150 lbs. for someone who is 5’5″. At 5’10”, a healthy BMI runs between 129 lbs. and 175 lbs. For adults ages 20 and older, a BMI of 30 and above is considered obese.
The previous charts for children did not go beyond a BMI of 37. The new charts extend to a BMI of 60 and measures whether it falls within healthy parameters based on a percentile measured against other children of the same age and gender.
“Prior to today’s release, the growth charts did not extend high enough to plot BMI for the increasing number of children with severe obesity,” said Dr. Karen Hacker, director of the CDC’s National Center for Chronic Disease Prevention and Health Promotion.
BMI for kids up to 20-year-olds runs along a sliding range, depending on age and gender. Under the new guidelines, healthy BMI for kids can range from as low as around 13 to about 17 for a 6-year-old girl or boy to a range of as much as roughly 18 to around 26 for a 20-year-old young woman.
The extended charts will help health-care providers work with families to treat children who are suffering from obesity, Hacker said. The BMI charts from 2000 will still be used for children who are not obese, according to CDC.
Obesity has increased significantly among children over the past 40 years. During the four year period ending in 1980, 5.5% of children ages 2 to 19 were obese and 1.3% were severely obese. By 2018, 19.3% of kids were obese and 6.1% were severely obese, according to National Center for Health Statistics.
Obesity for children is defined as a BMI that is higher than 95% of kids of the same age and gender, according to the CDC. Severe obesity is a BMI that is 120% higher than the 95th percentile.
Although children’s BMI is calculated using the same formula as adults, a healthy weight is measured in relation to other kids of the same age and gender. This is because children’s height and weight can vary significantly as they grow.